How 'we' came to be?
Evolution, forces were beneficial to our ancestors who adapted to the conditions at the time and they developed ways to make tools and luck of mutations provided a bigger brain to help figure out how to do these things.

Why we are here?
Evolution. Ask the same question about why holstein cattle are here. Evolution, in the case of the holsteins man was the force, in the case of homo sapiens climate conditions were the force.

Want to read up on more of our ancestors and how 'we' evolved? I was just looking through this article earlier so here is a link.

https://geneticliteracyproject.org/2023/05/04/why-africa-was-the-crucible-for-the-transition-of-early-humans-from-forest-inhabiting-fruit-eater-to-savanna-dwelling-hunter/?mc_cid=45ebd967b2&mc_eid=fb6767ee28

That humans originated in Africa is widely accepted. But it’s not generally recognised how unique features of Africa’s ecology were responsible for the crucial evolutionary transitions from forest-inhabiting fruit-eater to savanna-dwelling hunter. These were founded on earth movements and aided physically by Africa’s seasonal aridity, bedrock-derived soils and absence of barriers to movements between north and south.

These features promoted extensive savanna grasslands marked by erratic rainfall, regular fires and abundant numbers of diverse grazing and browsing animals.

My lifelong studies have focused on the ecology of Africa’s large herbivores and their effects on savanna vegetation. In my recent book, by linking pre-existing threads together for the first time, I explain how distinctive features of these animals’ ecology, founded on Africa’s physical geography, enabled the adaptive changes that led ultimately to modern humans.

What emerges is the realisation that this amazing evolutionary transformation could only have occurred in Africa. This recognition emphasises the deep cultural legacy formed by Africa’s large mammal heritage for all of humankind.